Irish moss is an alga having many stalks or fronds on a shallow root system, the moss generally growing on a rocky sea bottom since it attaches itself to the surface of rocks by a disc-like holdfast. The frond divides repeatedly to form a bushy head, the frond being tough and resilient and having an overall length of three to five inches.
Many attempts have been made in the past to harvest Irish moss, examples being found in U.S. Pat Nos. 2,941,344 (Jertson, June 21, 1960) and 3,540,194 (Chaplin, Oct 2, 1968). Each of these patents illustrates complex structures using a continuous conveyor mechanism which either combs the plants to cut them from the substrate (Jertson) or extracts the entire plant from the substrate (Chaplin), the conveyors carrying the harvested plants to the surface. The Chaplin structure also carries much of the substrate to the surface, disrupting the substrate sufficiently to make new growth difficult. The Jertson structure uses flat comb-like rake member which rid over the substrate. Single rakes of similar construction are considered to have a detrimental effect on the Irish moss resource.